Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Peer Reviewed
See detailPHOTOREDUCTION OF PROTOCHLOROPHYLLIDE IN DARK-GROWN BEAN COTYLEDONS AS A FUNCTION OF AGE
SCHOEFS, B.; Bertrand, Marie-Christine ULg; Garnir, Henri-Pierre ULg et al

in Murata, N (Ed.) Research in Photosynthesis (1992)

Detailed reference viewed: 1 (0 ULg)
Full Text
Peer Reviewed
See detailPHOTOREDUCTION OF PROTOCHLOROPHYLLIDE TO CHLOROPHYLLIDE IN 2-D-OLD DARK-GROWN BEAN (PHASEOLUS-VULGARIS CV COMMODORE) LEAVES - COMPARISON WITH 10-D-OLD DARK-GROWN (ETIOLATED) LEAVES
SCHOEFS, B.; Franck, Fabrice ULg

in Journal of Experimental Botany (1993), 44(263), 1053-1057

Two-d-old leaves which do not contain prolamellar bodies synthesize active protochlorophyllide in darkness. When protochlorophyllide is photoreduced by one intense white flash, a main chlorophyllide ... [more ▼]

Two-d-old leaves which do not contain prolamellar bodies synthesize active protochlorophyllide in darkness. When protochlorophyllide is photoreduced by one intense white flash, a main chlorophyllide species emitting at 690 nm is formed. After the photoreduction, the emission maximum is shifted to 675 nm within 5 s. This result suggests that in young leaves, chlorophyllide formed after one flash is quickly released from the active site of NADPH: protochlorophyllide oxidoreductase. This interpretation is strenghtened by time-resolved fluorescence measurements at room temperature, showing that 675 nm emitting chlorophyllide does not transfer excitation energy to the 696 nm emitting chlorophyllide which is formed in very low amount. In 10-d-old bean leaves, the 690 nm chlorophyllide emitting species formed after one short flash undergoes the well-known rapid and Shibata spectral shifts. The 675 nm emitting chlorophyllide appears only as a shoulder. At both ages, the fluorescence intensity of the active protochlorophyllide strongly decreases during and after photoreduction, suggesting rapid modifications in the close environment of the pigment. [less ▲]

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
See detailThe photorefractive effect at large modulation depth in semiconductors with multiple defect levels
Nguyen, Ngoc Duy ULg; Schmeits, Marcel ULg

in Applied Physics B : Lasers & Optics (2002), 74

The photorefractive effect in semiconducting mate- rials with multiple defects is studied in the case of modulation depth m = 1. The basic equations are Poisson's equation and the continuity equations for ... [more ▼]

The photorefractive effect in semiconducting mate- rials with multiple defects is studied in the case of modulation depth m = 1. The basic equations are Poisson's equation and the continuity equations for electrons, holes and occupied defect levels. They include all recombination and optical generation mechanisms between the defect levels and valence and conduc- tion bands. Their explicit numerical solution yields microscopic quantities such as space- and time-dependent electrical field profiles, carrier concentrations, as well as generation and re- combination rates. The fundamental Fourier component of the electric field yields the two-wave-mixing gain. Application is made for InP with two levels in the forbidden gap, for which steady-state and transient resulting quantities are shown. The re- sulting features at large modulation depth are of non-sinusoidal shape. Due to the complexity of the system, the final results strongly depend on all parameters intervening in the models used, as is illustrated for several typical cases. [less ▲]

Detailed reference viewed: 20 (4 ULg)
Full Text
See detailPhotorefractive holographic interferometry for movable artwork assessment
Thizy, Cédric ULg; Georges, Marc ULg; Koulompi, Eleni et al

in Hesselink, Lambertus; Feinberg, Jack (Eds.) Controlling Light with Light: Photorefractive Effects, Photosensitivity, Fiber Gratings, Photonic Materials and More (PR07) (2007, October)

Photorefractive holographic interferometry is applied to assessment of movable cultural heritage. Its role is to observe tiny signatures resulting from internal artwork characteristics. In the future, the ... [more ▼]

Photorefractive holographic interferometry is applied to assessment of movable cultural heritage. Its role is to observe tiny signatures resulting from internal artwork characteristics. In the future, the system will be used for both antifraud and restoration [less ▲]

Detailed reference viewed: 26 (2 ULg)
Full Text
Peer Reviewed
See detailPhotorefractive ZnTe grown by traveling heater method
Verstraeten, David; Launay, Jean-Claude; Delaye, Philippe et al

in Trends in Optics and Photonics (2003), 87

Detailed reference viewed: 28 (7 ULg)
See detailPhotos + annonce de Colloque International, U. Lg
Sacré, Robert ULg

in Soul Bag (1991), (124),

1) PHOTO DE COUVERTURE Johnny Heartman 2) Photos Ann PEEBLES , Otis CLAY , Lynn WHITE ; Hasselt Nov. 1989 3) Annonce de la Conférence Internationale de Septembre 1991 à l' Université de Liège ( The ... [more ▼]

1) PHOTO DE COUVERTURE Johnny Heartman 2) Photos Ann PEEBLES , Otis CLAY , Lynn WHITE ; Hasselt Nov. 1989 3) Annonce de la Conférence Internationale de Septembre 1991 à l' Université de Liège ( The secular in religious music and the sacred in secular music" [less ▲]

Detailed reference viewed: 11 (0 ULg)
Peer Reviewed
See detailPhotosensitized generation of hydroxyl radical by eught new sulfur and selenium analogs of psoralen
Collet, A.; Hoebeke, Maryse ULg; Piette, J. et al

in Journal of Photochemistry and Photobiology B : Biology (1996), 35

comparative study by ESR of the hydroxyl radical generation by 8 eight new sulfur and selenium analogs of psoralen

Detailed reference viewed: 4 (2 ULg)
Peer Reviewed
See detailPhotosensitized Production of Singlet Oxygen by Merocyanine 540 Bound to Liposomes
Hoebeke, Maryse ULg; Piette, Jacques ULg; van de Vorst, A.

in Journal of Photochemistry and Photobiology B : Biology (1991), 9(3-4), 281-94

The production of singlet oxygen by merocyanine 540 was studied in dimyristoyl-phosphatidylcholine liposomes using two singlet oxygen probes: 9,10-anthracenedipropionic acid (water soluble) and 9,10 ... [more ▼]

The production of singlet oxygen by merocyanine 540 was studied in dimyristoyl-phosphatidylcholine liposomes using two singlet oxygen probes: 9,10-anthracenedipropionic acid (water soluble) and 9,10-dimethylanthracene (liposoluble). Upper and lower limits of singlet oxygen quantum yield for bound merocyanine 540 were determined to be 0.055 and 0.015 respectively. The diffusion characteristics of singlet oxygen were examined using the isotropic enhancement effect of D2O and the inhibitory effect of sodium azide. It was shown that 1O2 spent more than 87% of its lifetime in a vesicle environment. When the singlet-reacting substrate and the dye were both located in the bilayer, approximately 40% of the singlet oxygen remained in the liposomes where it was originally generated. [less ▲]

Detailed reference viewed: 17 (0 ULg)
Full Text
Peer Reviewed
See detailThe "photosphere-wind connection" in Wolf-Rayet stars: simultaneous photometry and spectroscopy of EZ CMa
Morel, Thierry ULg; St-Louis, N.; Marchenko, S. V.

in Liege International Astrophysical Colloquia (1996)

Not Available

Detailed reference viewed: 7 (3 ULg)
Full Text
Peer Reviewed
See detailPhotospheric abundance peculiarities in chromospherically active stars
Morel, Thierry ULg; Micela, G.; Favata, F.

in 13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun (2005, March 01)

Not Available

Detailed reference viewed: 8 (3 ULg)
Full Text
Peer Reviewed
See detailPhotospheric Abundance Peculiarities in RS CVn Binaries
Morel, Thierry ULg; Micela, Giuseppina; Favata, Fabio

in Astrophysics & Space Science (2006), 304

We discuss the results of a LTE abundance study of 14 single-lined RS CVn binaries. Increasingly peculiar abundance ratios are observed for the cooler and more active stars in this sample (this is best ... [more ▼]

We discuss the results of a LTE abundance study of 14 single-lined RS CVn binaries. Increasingly peculiar abundance ratios are observed for the cooler and more active stars in this sample (this is best illustrated in the case of oxygen). This may arise from the existence of large spot groups, departures from LTE much larger than anticipated and/or inadequacies in the Kurucz model atmospheres for these objects. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
Peer Reviewed
See detailThe photospheric abundances of active binaries. II. Atmospheric parameters and abundance patterns for 6 single-lined RS CVn systems
Morel, Thierry ULg; Micela, G.; Favata, F. et al

in Astronomy and Astrophysics (2003), 412

Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been ... [more ▼]

Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been derived for 13 chemical species, including several key elements such as Li, Mg, and Ca. Two methods have been used. The effective temperatures, surface gravities and microturbulent velocities were first derived from a fully self-consistent analysis of the spectra, whereby the temperature is determined from the excitation equilibrium of the Fe I lines. The second approach relies on temperatures derived from the (B-V) colour index. These two methods give broadly consistent results for the stars in our sample, suggesting that the neutral iron lines are formed under conditions close to LTE. We discuss the reliability in the context of chromospherically active stars of various colour indices used as temperature indicators, and conclude that the (V-R) and (V-I) colours are likely to be significantly affected by activity processes. Irrespective of the method used, our results indicate that the X-ray active binaries studied are not as metal poor as previously claimed, but are at most mildly iron-depleted relative to the Sun (-0.41protect <~ [Fe/H]protect la +0.11). A significant overabundance of several chemical species is observed (e.g., the alpha -synthezised elements). These abundance patterns are discussed in relation to stellar activity. Based on observations collected at ESO (La Silla, Chile). Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/412/495 [less ▲]

Detailed reference viewed: 13 (2 ULg)
Full Text
Peer Reviewed
See detailThe photospheric abundances of active binaries. III. Abundance peculiarities at high activity levels
Morel, Thierry ULg; Micela, G.; Favata, F. et al

in Astronomy and Astrophysics (2004), 426

We report the determination from high-resolution spectra of the atmospheric parameters and abundances of 13 chemical species (among which lithium) in 8 single-lined active binaries. These data are ... [more ▼]

We report the determination from high-resolution spectra of the atmospheric parameters and abundances of 13 chemical species (among which lithium) in 8 single-lined active binaries. These data are combined with our previous results for 6 other RS CVn systems to examine a possible relationship between the photospheric abundance patterns and the stellar activity level. The stars analyzed are generally found to exhibit peculiar abundance ratios compared to inactive, Galactic disk stars of similar metallicities. We argue that this behaviour is unlikely to be an artefact of errors in the determination of the atmospheric parameters or non-standard mixing processes along the red giant branch, but diagnoses instead the combined action of various physical processes related to activity. The most promising candidates are cool spot groups covering a very substantial fraction of the stellar photosphere or NLTE effects arising from nonthermal excitation. However, we cannot exclude the possibility that more general shortcomings in our understanding of K-type stars (e.g. inadequacies in the atmospheric models) also play a significant role. Lastly, we call attention to the unreliability of the (V-R) and (V-I) colour indices as temperature indicators in chromospherically active stars. Based on observations collected at the European Southern Observatory, Chile (Proposals 64.L-0249 and 071.D-0260). Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/426/1007 [less ▲]

Detailed reference viewed: 28 (2 ULg)
Full Text
See detailThe Photospheric Abundances of Active Binaries: First Results
Morel, Thierry ULg; Micela, G.; Favata, F. et al

in Stars as Suns : Activity, Evolution and Planets (2004, January 01)

The coronal abundances of chromospherically active binaries have come under close scrutiny in recent years thanks to several X-ray satellites such as XMM or Chandra. Unfortunately a detailed analysis of ... [more ▼]

The coronal abundances of chromospherically active binaries have come under close scrutiny in recent years thanks to several X-ray satellites such as XMM or Chandra. Unfortunately a detailed analysis of the chemical fractionation processes that are possibly operating between the photosphere and the corona is plagued by the lack of reliable and accurate photospheric abundance determinations. In particular a detailed investigation of the photospheric metal content seems worthwhile in the light of several studies that have questioned the customary use of photometric indices as effective temperature indicators in active binaries. We shall present our ongoing effort to determine in a self-consistent way accurate physical parameters and photospheric abundances for a large number of systems and discuss the implications of our results on their abundance patterns and evolutionary status. Preliminary results suggest that these systems are not as iron-deficient as found in previous studies and indicate an overabundance of several key elements (e.g. Na Mg Al Ca) with respect to the solar pattern. [less ▲]

Detailed reference viewed: 5 (1 ULg)
Peer Reviewed
See detailPhotostability studies of molsidomine-cyclodextrin complexes
Piel, Géraldine ULg; Pochet, Lionel; Delattre, Luc ULg et al

Poster (1995, June)

Detailed reference viewed: 19 (0 ULg)
Full Text
See detailLa photosynthèse: aujourd'hui, hier et demain
Franck, Fabrice ULg

Conference (2012, November 30)

Detailed reference viewed: 32 (8 ULg)
Full Text
Peer Reviewed
See detailPhotosynthesis and state transitions in mitochondrial mutants of Chlamydomonas reinhardtii affected in respiration
Cardol, Pierre ULg; Gloire, Geoffrey ULg; Havaux, M. et al

in Plant Physiology (2003), 133(4), 2010-2020

Photosynthetic activities were analyzed in Chlamydomonas reinhardtii mitochondrial mutants affected in different complexes (I, III, IV, I + III, and I + IV) of the respiratory chain. Oxygen evolution ... [more ▼]

Photosynthetic activities were analyzed in Chlamydomonas reinhardtii mitochondrial mutants affected in different complexes (I, III, IV, I + III, and I + IV) of the respiratory chain. Oxygen evolution curves showed a positive relationship between the apparent yield of photosynthetic linear electron transport and the number of active proton-pumping sites in mitochondria. Although no significant alterations of the quantitative relationships between major photosynthetic complexes were found in the mutants, 77 K fluorescence spectra showed a preferential excitation of photosystem I (PSI) compared with wild type, which was indicative of a shift toward state 2. This effect was correlated with high levels of phosphorylation of light-harvesting complex II polypeptides, indicating the preferential association of light-harvesting complex II with PSI. The transition to state 1 occurred in untreated wild-type cells exposed to PSI light or in 3-(3,4-dichlorophenyl)-1,1-dimethylurea-treated cells exposed to white light. In mutants of the cytochrome pathway and in double mutants, this transition was only observed in white light in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. This suggests higher rates of non-photochemical plastoquinone reduction through the chlororespiratory pathway, which was confirmed by measurements of the complementary area above the fluorescence induction curve in dark-adapted cells. Photo-acoustic measurements of energy storage by PSI showed a stimulation of PSI-driven cyclic electron flow in the most affected mutants. The present results demonstrate that in C. reinhardtii mutants, permanent defects in the mitochondrial electron transport chain stabilize state 2, which favors cyclic over linear electron transport in the chloroplast. [less ▲]

Detailed reference viewed: 37 (9 ULg)
Peer Reviewed
See detailPhotosynthesis in picoeucaryote algae, the Ostreococcus case
Cardol, Pierre ULg

Conference (2007, June 19)

Detailed reference viewed: 14 (0 ULg)